The present invention relates to a device whereby a particular item may be specified, from a number of other items, by an operator manually generating an electrical signal to designate that particular item. The signal thus generated may for example be input to a computer or other data processing system, as a data input. One method of accomplishing this is to write or print data designating each of the items in predetermined positions, e.g. in a matrix array configuration, on each of a plurality of flexible sheets, and to roll these sheets in a successively overlapping manner around a cylindrical sheet holder. Means can then be provided, as will be made clear hereinafter by embodiments of the present invention, whereby a particular sheet can rapidly be selected and unrolled to be positioned below a keyboard having flexible keys arranged in positions corresponding to the items on the flexible sheet. Actuation of a key corresponding to a desired item can then generate a signal designating that item. Such an apparatus has a number of advantages, including ease and rapidity of selecting a desired item, and simplicity of use, with no special operator skills being required. However, if it is desired to change the information provided on a sheet, either partially or completely, then it is necessary either to completely remove the sheet in question, or to erase items from that sheet and write in new items. This can be troublesome and time-consuming. In addition, since there will generally be some degree of contact between a sheet, when it is selected and unrolled, and other parts of the apparatus, the resultant friction will eventually result in partial or complete erasure of the information recorded on a sheet.
There is therefore a requirement for an apparatus of the general form described above, which would not present the disadvantages related in the preceding paragraph, yet which would retain the considerable advantages offered by such a multi-item data input apparatus of the form described above. This requirement is achieved by a multi-item data input apparatus according to the present invention, as will be described in the following, with respect to specific embodiments.